1. Field of the Invention
The present invention relates to optical element support structures and methods of making the same.
2. Description of the Related Art
A physical object, such as an optical fiber 900 in FIG. 9, possesses at least six positional degrees of freedom (DOFs), e.g., in Cartesian space, the six DOFs are X, Y, Z, xcex8X, xcex8Y, xcex8Z. The problem in any optical device is the constraint/specification of optically critical DOFs of various optical elements such that the elements are in alignment, thereby allowing the transmittance of light in an acceptable manner.
Typical optical elements such as rod lenses and fiber tips are usually circularly symmetric (shown about the Z axis in FIG. 9) and therefore require only five constrained DOFs to completely specify their positions (xcex8Z is the unnecessary DOF).
Conventional fiber support structures often fail to accurately align fibers to desired positions, particularly where fibers vary in diameter due to manufacturing tolerances. Conventional fiber support structures also allow fibers to move undesirably prior to bonding.
In the milieu of small electro-optical and optomechanical devices, such as MicroElectroMechanical System (MEMs) optical devices, modulated laser transmitters and photodiode receivers for the telecommunications industry, fibers have been positioned for years using V-grooves in a silicon structure, or some variant thereof. FIG. 10 illustrates four DOFs of a fiber 900 controlled by a V-groove 1002 in a silicon structure 1000. The Z position is usually defined/controlled by either butting the end of the fiber 900 against another component or a micromachined stop, or by polishing one end 902 of the fiber 900 to some known reference position.
One drawback to the structure 1000 in FIG. 10 is the necessity of some external mechanical implement to hold the fiber 900 in the V-groove 1002 prior to bonding or soldering.
Another drawback is the lack of position compensation for changes in the diameter of a fiber 900, as shown in FIG. 11. FIG. 11 illustrates a maximum fiber diameter 1100 and a nominal fiber diameter 1102. An increase in diameter of 2 microns (typical range of manufacturing tolerance) would translate the core 1104 of the fiber 900 (the critical optical portion) in the Y direction by 1.73 microns (1 micron on the radius times 1/COS(54.74 degrees)). This variance may be unacceptable in some applications.
For lenses, the manufacturing tolerance range is much larger, e.g., on the order of 15 microns. Fortunately, positioning accuracy requirements may be somewhat less stringent for lenses.
Optical element support structures and methods of using and making the same are provided in accordance with the present invention. The optical element may be a lens, a rod lens, a fiber, a fiber end, a mirror or some other object, e.g., a holder for an optical component. The lens and fiber support structures may also be referred to herein as fiber or lens xe2x80x98chucks.xe2x80x99
The support structures according to the invention may provide a number of advantages. For example, a support structure may temporarily restrain and align an optical element in a mounting wafer/substrate with a high degree of lateral centration. The optical element may or may not be glued to the support structure, depending on the desired level of constraint for an application. Lateral centration is measured by how close a center axis of an optical element, where it crosses an upper surface of the wafer, comes to a pre-determined point, e.g., the center of a hole, on that surface.
As another example, a support structure may also temporarily restrain and align an optical element in a mounting wafer such that the axis of the optical element is extremely close to a normal vector of the wafer surface. In some applications, it is desirable to have lateral centration within one micron, and alignment to the surface normal within 5 arcminutes. After the structure restrains the optical element, the element may be glued or bonded in place.
As another example, a support structure may also accommodate (or compensate for) variations or imperfections in the diameter of a fiber or lens, e.g., up to a couple microns for optical fibers or up to tens of microns for rod lenses. This characteristic may be called xe2x80x98tolerancexe2x80x99 for diameter imperfections. The support structures may also accurately restrain and align fiber ends and rod lenses after static deformation due to heat.
One aspect of the invention relates to a support structure configured to restrain an optical element in at least two degrees of freedom. The structure comprises a first jaw, a first flexure, a second jaw and a second flexure. The first jaw has a first jaw face configured to contact the optical element. The first flexure is attached to the first jaw. The second jaw has a second jaw face configured to contact the optical element. The second flexure is attached to the second jaw. The first jaw face and the second jaw face are configured to restrain the optical element in at least two degrees of freedom.
Another aspect of the invention relates to a method of forming an optical element support structure. The method comprises using radiation and a patterned mask to affect pre-determined areas of a photo-sensitive film on a substrate. The mask outlines a first jaw with a first jaw face configured to contact the optical element, a first flexure attached to the first jaw, a second jaw with a second jaw face configured to contact the optical element, and a second flexure attached to the second jaw. The first jaw face and the second jaw face are configured to restrain the optical element in at least two degrees of freedom. The method further comprises using a micromachining process to form the first jaw, first flexure, second jaw and second flexure in the substrate based on the mask outline.